Screen printing as a printing process is widely used in repetitive printing of images on many types of media such as paper, fabric, ceramics, and so forth, and is applicable to printing with inks of many types, ranging from coloring dyes to inks containing reflecting beads and metallic powders having controlled electrical characteristics, and many other ingredients serving specific purposes.
In conventional screen printing, one of the most annoying and costly occurences in long run screen printing production is the "pinholding (i.e. forming of pinholes)" and the ultimate breakdown of the screen stencil.
This most frequently occurs when water based inks are used with water base photo emulsion screens. It also occurs with screens that are frequently washed up and inventoried for use at a later date. Nothing damages a screen stencil more than the washup process used for removing remaining ink before storing the stencil for future use.
On multi-thousand runs using water based inks, the emulsion starts to pinhole (i.e. form pinholes) and generally break down after a limited number of printing cycles due to wear on the screen and from the frequent washing after each printing run. This means production must stop while the stencil is temporarily retouched or possibly remade.
The method and composition according to the instant invention eliminates this costly occurrence. This system as disclosed can be used with all photo stencil methods, and preferably with the direct or the indirect method of the direct-indirect method, and other photo stencil preparation methods.
It is accordingly an object of the instant invention to provide a method of overcoming the problem of pinholing in screen stencils after prolonged use and to provide a sealing composition to be used for the method.